The present invention relates to an image processing method and apparatus, such as a scanner into which a document image is digitally read by a CCD element and the like and from which the image is outputted, a copying apparatus and a facsimile using the scanner, and especially relates to an image processing apparatus by which the characteristic of the image is selected, and from which the image is outputted while processing is selectively changed even in one image plane.
Recently, as the amount of information which is exchanged and transmitted has increased, an enormous amount of printed documents are further copied and transmitted by a copying apparatus or facsimile. In the image which is copied and transmitted as described above, documents in which different textures such as characters and pictures are mixed, have also increased. In the copying apparatus and facsimile which read in, process and output images, it is more advantageous for an increase of the output image quality and the transmission efficiency to process them and change-over parameters of processing according to the texture of these images. For example, in the copying apparatus, it is necessary to change-over a gamma correction unit or a filter according to a character or a photographic image, and in the facsimile, it is necessary to change-over a coding method. Accordingly, a mechanism which selects an image characteristic automatically and outputs it at each pixel with image data, is required for a processing apparatus.
Various kinds of these discrimination methods have been proposed conventionally. However, in many cases, these are methods in which the image is divided into small areas, and image characteristics are successively judged by a small window. In these cases, the image can be processed without observing the entire image, and therefore, approximates real time processing can be conducted. However, there are many types of apparatus in the prior art which detect the character image basically by a space differentiation (an edge finding procedure) conducted in the window, and thereby there is a tendency that an error occurs frequently in which a halftone image is misjudged as a character image depending on a read-out resolution.